The present invention relates to an image sensing system and method thereof, and more particularly to a low Random Telegraph Signal (RTS) noise image sensor and method thereof.
A Charge-coupled Device (CCD) or a complementary metal-oxide-semiconductor (CMOS) image sensor (CIS) has been commonly used in an image capturing device, such as a camera. In comparison to CCD sensors, CIS sensors have faster readout, more functions, and a smaller system size. However, CIS sensors may suffer from noise induced by Random Telegraph Signals (RTS). RTS noise is caused by charges trapped in the gate-oxide region of a field-oxide transistor. RTS noise has become an issue for low light level applications, especially in downscaling transistor dimensions. For example, RTS noise can greatly affect the image quality of the camera. Apart from the RTS noise, in some existing methods, a circuit used for reading the signal of CIS sensors occupies a relatively large area and consumes way too much power from the camera due to the high resolution of CIS pixels and high-speed imaging requirements.